linux-kernel - [PATCH 06/25] serial: sh-sci: Don't overwrite clock selection in serial_console

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Date:	Thu, 19 Nov 2015 19:38:45 +0100
From:	Geert Uytterhoeven <geert+renesas@...der.be>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Simon Horman <horms@...ge.net.au>,
	Magnus Damm <magnus.damm@...il.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>
Cc:	linux-serial@...r.kernel.org, linux-sh@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH 06/25] serial: sh-sci: Don't overwrite clock selection in serial_console_write()

Blindly writing the default configuration value into the SCSCR register
may change the clock selection bits, breaking the serial console if the
current driver settings differ from the default settings.

Keep the current clock selection bits to prevent this from happening
on e.g. r8a7791/koelsch when support for the BRG will be added.

Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
 drivers/tty/serial/sh-sci.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 7c7dfbce54ed9c19..cba51da604253db6 100644
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -2415,7 +2415,7 @@ static void serial_console_write(struct console *co, const char *s,
 {
 	struct sci_port *sci_port = &sci_ports[co->index];
 	struct uart_port *port = &sci_port->port;
-	unsigned short bits, ctrl;
+	unsigned short bits, ctrl, ctrl_temp;
 	unsigned long flags;
 	int locked = 1;
 
@@ -2427,9 +2427,11 @@ static void serial_console_write(struct console *co, const char *s,
 	else
 		spin_lock(&port->lock);
 
-	/* first save the SCSCR then disable the interrupts */
+	/* first save SCSCR then disable interrupts, keep clock source */
 	ctrl = serial_port_in(port, SCSCR);
-	serial_port_out(port, SCSCR, sci_port->cfg->scscr);
+	ctrl_temp = (sci_port->cfg->scscr & ~(SCSCR_CKE1 | SCSCR_CKE0)) |
+		    (ctrl & (SCSCR_CKE1 | SCSCR_CKE0));
+	serial_port_out(port, SCSCR, ctrl_temp);
 
 	uart_console_write(port, s, count, serial_console_putchar);
 
-- 
1.9.1

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